In a previons paper irdin this instilitle (Melin 1954 a), it has been demonstrated that exci.sed pine and tomato roots exert a strong growth-promoting eltect oti In'i! mycorrhizal fnngi growing in media containing sngar, salts, \il;imiii,s and amino aeids. It was coneltided tliat the roots prodttce one or mure growth-pronioting metabolites, ctHiveniently called factor M (Melin 1954b), which are essential to the growth of the fungi eoncerned.Tbe experiments reported behiw bave been performed with a view lo find otit if these metabolites have a wide-spread oecnrrence in a wide variety of rools, and to get a deeper nnderstanding of their physiological effect on the Jiingi. Accordingly, we have stttdied the itifluences of root-metaboiiles of plants whicb are f]uile distantly iclaled to each otber. As well as tomato [Solfinum Lijeopersieaui L.], the following plants wore u.sed in tbe experiments: Lepidium satiuuin L., Medicago satiua L., Canwdns sutiva L., Pisutn .satiuutn L. and Tritieutn aestii)iiin L.. Tliell.

The use of antitranspirants may guarantee the establishment of seedlings transplanted under drought conditions or prolong the life of mature plants at sub-optimal moisture levels. Where water is really scarce they can reduce transpiration losses to the extent that irrigation intervals may be extended. Whilst, at present, known antitranspirants are relatively expensive, their use can be justified, for example, to prevent shrinkage in high-value fruits, or where crop survival is threatened.Plants need water; but they are profligate in its use. Roughly 1% of the water taken up by a plant is used for its growth and development while the remaining 99% is lost by transpiration. Whilst drainage and evaporation playa considerable part in water loss, it is clear that much of the water applied in irrigation is lost through transpiration alone. Often the rate of transpiration exceeds that of water absorption (particularly under conditions of high evaporative demand, and even when soil water is readily available) and the resultant water stress restricts plant growth. Reduction of transpiration, were it feasible, could minimize the irrigation water requirement and thus relieve the plant from water stress to a certain extent.

With Plate 12 and 8 figures in the text)It has been realized for some time that the catalysts of respiration must be spatially separated and organized within plant cells, and numerous recent studies have confirmed that they may be distributed among different organelles. Particular attention has been given to the oxidizing systems present in mitochrondria, and their behaviour in colourless cells elucidated at least in outline. Since respiration occurs also in chlorophyllous cells, and its links with photosynthesis are open to some doubt, it becomes a matter of interest to know whether chloroplasts respire, and whether they borrow products of respiration from other components of the cell. MATERIALYoung leaves of Windsor-type broad beans were taken from plants three to six weeks old. During the spring and summer the plants were grown on plots in the open; during the cold weather they were raised in pans of soil in a frost-free greenhouse. Spinach beet (Swiss Chard) was also grown out of doors, and was available for most of the year.The leaves were picked shortly before the experiment and were washed first under the tap and then rinsed with distilled water and blotted dry. They were next kept in a refrigerator for two to three hours to bring them to 2° C. before maceration. Entire leaflets of broad bean were used; but the large midribs and main veins of the spinach beet were removed after chilling and immediately before blending. METHODS HomogenizationThe leaves were homogenized in a Waring Blender held at -3° C. in a cold chest with a small top opening. Forty to forty-five gm. chilled broad bean leaf was torn up by hand and dropped into the pot of the blender. About 100 ml. medium, also chilled, was added and the blender run at maximum speed (11,000 RPM) for three consecutive periods of 10 sec. with short breaks between to prevent rise of temperature. The leaf mash was then strained through muslin without removal from the cold box. The same procedure was followed with spinach beet leaves; but about 60 gm. leaf was taken to allow for the discarding of the heavy veins.The medium employed was made up fresh for each experiment and cooled to 2° C. It contained 0.3M sucrose; 0.067M phosphate to give pH 7.3; i.8xio-=M MgSO, and 2 X io-'M versene. In some experiments on soluble enzymes this medium was replaced by 0.35M NaCl as recommended by Arnon et al. (1956). 325

ABSTRACITwo naturally occurring species of the genus Alternanthera, namely A. ficoides and A. tenella, were identified as C3-C4 intermediates based on leaf anatomy, photosynthetic CO2 compensation point (r), 02 response of r, light intensity response of r, and the activities of key enzymes of photosynthesis. A.

SUMMARY Benzyl adenine enhanced stomatal opening in isolated epidermal strips of Commelina benghalensis and Tridax procumbens. The stimulation was maximum at a concentration of 5 × 10‐5 M BA. But kinetin had no remarkable effect on stomatal opening. The activity of benzyl adenine was observed over a narrow range of concentrations, from 10‐5 M to 10‐4 M. The increase in stomatal aperture was more pronounced in Commelina than in Tridax. Presence of benzyl adenine in the medium prevented the stomatal closure expected from abscisic acid and could reverse considerably the stomatal closure induced earlier by abscisic acid. It is felt that the balance between abscisic acid and cytokinins can possibly control the stomatal aperture effectively.

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SUMMARYThe effect of 0 to 100/iM bicarbonate on stomatal opening in epidermal strips of Commelina benghalensis was examined in the presence or absence of fusicoccin in light or darkness. Low concentrations of bicarbonate (up to 10 /iM in the absence and 25 fiM in presence of fusicoccin) stimulated stomatal opening while higher concentrations inhibited. The enhancement of opening by low concentrations of bicarbonate and phosphoenol pyruvate (PEP), and prevention of bicarbonate stimulation by malate or oxaloacetate suggested PEP carboxylase as a CO2 sensor in the guard cells. However, the inhibition of PEP carboxylase did not completely suppress the opening caused by fusicoccin. The action of fusicoccin therefore appears to involve a site other than CO2 fixation, presumably through the stimulation of proton excretion.

No abstract